In providing electrical circuits to a facility, such as a home, one or more branch circuits are wired to distribute electrical power to load devices, such as outlet receptacles or light fixtures. Typically, the receptacle or fixture is hardwired directly to the branch circuit, with power to the device being turned on or off at the device itself. For example, a light fixture might include a pull cord for actuating a switch, while a small appliance might include a power switch.
With recent technological developments it is both possible and advantageous to provide automated control of load devices to provide, for example, remote or timed switching. One such system directs all communication functions into a system controller. This gives a home owner flexible communication and power control from anywhere in the home there is a control panel or switch, or even anywhere there is a telephone, such as the car or office. An intelligent outlet receptacle allows individual appliances to be separately and automatically controlled as necessary or desired. To do so, some means must be provided for controlling switching of power to an electrical outlet receptacle. A practical switching device must be inexpensive and reliable. A latching relay has been found to be readily adaptable to such an application. A latching relay is latched when connected to a positive polarity voltage source and unlatched when connected to a negative polarity voltage source.
Some applications require that electrical power be applied to an outlet receptacle only when in use. Particularly, the outlet receptacle is disconnected from the power source when no plug is present and disconnected to the power source when a plug is inserted in the receptacle. In combination with the above-described features, such a control circuit enables a particular outlet receptacle to be controlled both in response to presence or absence of a plug and demands of external user or automatic control functions.
An automatic control such as described requires that insertion of a plug be detected and an electronic signal be delivered to a control to indicate presence or absence of the plug. While inserting or removing the plug, it is possible that the sensing system could cycle, resulting in relay "chatter". Obviously, it is desirable to prevent relay chatter.
The present invention is directed to solving one or more of the problems discussed above in a novel and simple manner.